1. Field of the Invention
The present invention relates to an image forming apparatus.
2. Description of Related Art
Electrophotographic image forming apparatuses perform adjustment to maintain image qualities to be constant by forming reference images for image quality adjustment on sheets and changing image forming conditions and such like according to read values obtained by reading the reference images with reading sections (for example, see Japanese Patent Application Laid-Open Publication Nos. 2008-8967 and 2004-198947).
When image reading is performed by using a conventional CCD line sensor, phenomenon (flare) which negatively affects read values is generated in some cases due to emitted light being reflected at a position other than the reference image and entering the CCD. The phenomenon markedly occurs especially in a case where there is a large difference in luminosity (brightness) between adjacent color patches and in a case where a large difference in luminosity occurs due to a color patch of high density arranged on a white sheet. As for image reading using a CCD line sensor, flare has a great tendency to occur in a main scanning direction.
Thus, there have been methods of reducing reflected light from a position other than the image in order to reduce the flare in the main scanning direction. The methods of reducing reflected light from a position other than the image include, for example, a method of coating the inside of the unit with black matte and a method of suppressing reflection of optical system by narrowing an irradiation hole of a light source or providing antireflection coat to a cover glass.
However, it is difficult to completely eliminate reflected light from a position other than image and it is very difficult to completely suppress the flare by the above methods. Thus, even if the above methods are used, there is still a problem that the accuracy of color reproducibility is lowered when the difference in luminosity is large between adjacent color patches or between a high density color patch and a ground color of sheet.